#include<stdio.h>
int main()
{
    int a,b,c,d,e,f,g;
    scanf("%d:%d %d:%d",&a,&b,&c,&d);
    e=a*60+b;
    f=c*60+d;
    if(e>f)g=e-f;
    else g=f-e;
    printf("%d:%d",g/60,g%60);
    return 0;
}
